1. Field of the Invention
This invention relates generally to a method of assigning a frequency channel to a mobile unit in a mobile communications system, and more specifically to such a method which features effective reduction of interchannel interference with the result of efficient use of frequency spectrum. Further, this invention relates to a method of reassigning frequency channels currently allocated to a plurality of mobile units.
2. Description of the Prior Art
A mobile communications system including mobile-telephone services, has adopted a so-called multichannel access technique wherein when a mobile unit within a given cell requests channel access or a land site wishes to initially access a mobile unit, one is selected from a plurality of channels and is assigned to the mobile unit. According to a known technique, such a channel is randomly selected in response to each call requirement. Consequently, the conventional technique requires a sufficiently wide channel interval in order to prevent interference from adjacent channels.
With the increasing number of subscribers, the demand for narrowing the channel interval to accommodate more channels within a limited spectrum has increased markedly. However, the above-mentioned random channel selection inherently requires a large channel space and hence is unable to meet this requirement.